When to fill your air tank??

OK, I read through lots of this forum trying to find out some info as to when should you fill your tank back up. I have a 65 cu.ft tank 4500 psi/ How low should I let the psi go down to, before I go get it filled again and the reasoning why. A fired of mine told me he fills his when it goes down from 4500 to 3000. I sent him a email asking why but he is busy so I put the question up here. maybe common sense tells me that letting the air too low it will start to have moisture problems?? I was going to run it down till it emptied, but now I need to ask. My fills cost me 6 bucks, no matter what the gauge is at when I bring it in to have filled
 
Just filled my 87cf tank today. I run my tank till it is about 3800 to 4000psi and then put it on the Shoebox Max ... takes about 2-3 hours and when it is at 4500+ and I cut it off.. I don't let my guns run down much either ....~3000 to 2300psi and then fill. For me this works out, I use 90 % my guns for hunting and I'm only planning going to shoot maybe 16+ shots at the most. If I'm shooting cans in the back yard or messing around, in all honesty ... I use a springer/gas ram gun.

I very well may buy a 12fpe Maximus in 177 for messing around .... no recoil, no cocking and lots of shots. 12 fpe is fine for cans and an occasional starling ;- )

wll2506
 
"JohnL57"If you have multiple tanks you can "Cascade" to get more use out of your air. Start filling the gun with the tank that has the least pressure-fill to the maximum, then bleed the hose and top off with the higher pressure tank. You can use the lower pressure tank till it's at the minimum fill pressure you gun uses.
That is a great idea Thanks